Chiral N-Heterocyclic Carbene/Pyridine Ligands for the Iridium-Catalyzed Asymmetric Hydrogenation of Olefins


  • Financial support from the Swiss National Science Foundation is gratefully acknowledged. We thank Dr. Markus Neuburger (Laboratory for Chemical Crystallography, University of Basel) for the crystal structure analyses.


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Swapping N,P for C,N: Iridium complexes of bidentate pyridine-based C,N ligands with an N-heterocylic carbene (NHC) unit proved to be efficient and highly enantioselective hydrogenation catalysts. As a result of the lower acidity of iridium hydride intermediates produced from NHC-based complexes, these catalysts are much better suited than analogous N,P-ligand complexes for the hydrogenation of acid-sensitive substrates.